Asymmetric Transfer Hydrogenation of Ketones Catalyzed by Enantiopure Osmium(II) Pybox Complexes

Vega, Esmeralda; Lastra, Elena; Gamasa, M. Pilar

doi:10.1021/ic400680r

Cited by 30 publications

(15 citation statements)

References 21 publications

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“…In 2013, Gamasa's group 469 . When the reaction of acetophenone was conducted in 2-PrOH at 82°C in the presence of 0.6 mol % 116 and 12% KO t Bu, the corresponding alcohol was produced with 96−99% conversion and 86−94% ee.…”

Section: Osmium-based Catalystsmentioning

confidence: 99%

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The Golden Age of Transfer Hydrogenation

2015

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Section: Osmium-based Catalystsmentioning

confidence: 99%

“…To probe the applicability scope of the catalysts, a series of aromatic ketones with various substituents were examined in the catalytic system, and within 60 min the desired alcohol products were obtained with nearly complete conversion and 54−94% ee. 469 2.1.4. Cobalt-Based Catalysts.…”

Section: Osmium-based Catalystsmentioning

confidence: 99%

The Golden Age of Transfer Hydrogenation

2015

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“…The first examples of osmium complexes for asymmetric transfer hydrogenation (and the reverse reaction of alcohol oxidation) were reported by Faller et al., using cis ‐aminoindanol as the chiral ligand 6. Several chiral Os II complexes have been reported for asymmetric reductions including those containing L ‐α‐amino carboxylates7 and pybox ligands 8. Monophosphinite complexes,9 iminopyridine complexes,10 and pincer complexes11 have also been described.…”

Section: Reduction Of Prochiral Ketones 6–10 By Rr Pre‐catalysts 4 Amentioning

confidence: 99%

Easy To Synthesize, Robust Organo‐osmium Asymmetric Transfer Hydrogenation Catalysts

Coverdale

Sanchez‐Cano

Clarkson

et al. 2015

Chemistry A European J

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Asymmetric transfer hydrogenation (ATH) is an important process in organic synthesis for which the Noyori‐type RuII catalysts [(arene)Ru(Tsdiamine)] are now well established and widely used. We now demonstrate for the first time the catalytic activity of the osmium analogues. X‐ray crystal structures of the 16‐electron OsII catalysts are almost identical to those of RuII. Intriguingly the precursor complex was isolated as a dichlorido complex with a monodentate amine ligand. The OsII catalysts are readily synthesised (within 1 h) and exhibit excellent enantioselectivity in ATH reactions of ketones.

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“…23 Complex 61 proved to be an excellent TH catalyst in 2-propanol without base, while the chloride complex 60 was similarly active under basic Gamasa and co-workers very recently reported the synthesis and catalytic application of osmium(II)−pybox complexes 64− 67 bearing phosphine and phosphite ligands (Schemes 27 and 28). 24 In the ATH of acetophenone, Os complexes with (S,S)-iPr-pybox were more active than those with (R,R)-Ph-pybox, in the opposite way to the analogous Ru complexes. 25 After optimization of the reaction conditions, the (S,S)-iPr-pybox complexes 64a−d were examined in the reduction of a number of aryl alkyl ketones.…”

Section: Accounts Of Chemical Researchmentioning

confidence: 98%

Recent Advances in Osmium-Catalyzed Hydrogenation and Dehydrogenation Reactions

2015

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CONSPECTUS: A current issue in metal-catalyzed reactions is the search for highly efficient transition-metal complexes affording high productivity and selectivity in a variety of processes. Moreover, there is also a great interest in multitasking catalysts that are able to efficiently promote different organic transformations by careful switching of the reaction parameters, such as temperature, solvent, and cocatalyst. In this context, osmium complexes have shown the ability to catalyze efficiently different types of reactions involving hydrogen, proving at the same time high thermal stability and simple synthesis. In the catalytic reduction of C═X (X = O, N) bonds by both hydrogenation (HY) and transfer hydrogenation (TH) reactions, the most interest has been focused on homogeneous systems based on rhodium, iridium, and in particular ruthenium catalysts, which have proved to catalyze chemo- and stereoselective hydrogenations with remarkable efficiency. By contrast, osmium catalysts have received much less attention because they are considered less active on account of their slower ligand exchange kinetics. Thus, this area remained almost neglected until recent studies refuted these prejudices. The aim of this Account is to highlight the impressive developments achieved over the past few years by our and other groups on the design of new classes of osmium complexes and their applications in homogeneous catalytic reactions involving the hydrogenation of carbon-oxygen and carbon-nitrogen bonds by both HY and TH reactions as well as in alcohol deydrogenation (DHY) reactions. The work described in this Account demonstrates that osmium complexes are emerging as powerful catalysts for asymmetric and non-asymmetric syntheses, showing a remarkably high catalytic activity in HY and TH reactions of ketones, aldehydes, imines, and esters as well in DHY reactions of alcohols. Thus, for instance, the introduction of ligands with an NH function, possibly in combination with a pyridine ring, led to a new family of [OsCl2(PP)(NN)] (NN = diamine, 2-aminomethylpyridine; PP = diphosphine) and pincer [OsCl(CNN)(PP)] (HCNN = 6-aryl-2-aminomethylpyridine, 2-aminomethylbenzo[h]quinoline) complexes, which are outstanding catalysts for (asymmetric) HY and TH of carbonyl compounds and DHY of alcohols with turnover numbers and turnover frequencies up to 10(5) and 10(6) h(-1), respectively. In addition, PNN osmium complexes containing the 2-aminomethylpyridine motif have been found to be among the most active catalysts for HY of esters. These complexes have shown catalytic activities that are comparable and in some cases superior to those reported for analogous ruthenium systems. These results give an idea of the potential of Os complexes for the design of new highly productive and robust catalysts for the synthesis of chiral and nonchiral alcohols and amines as well as ketones from alcohols. Thus, we hope that this report will promote increased interest in the chemistry of these metal complexes, opening novel opportunities for new catalyti...

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Asymmetric Transfer Hydrogenation of Ketones Catalyzed by Enantiopure Osmium(II) Pybox Complexes

Cited by 30 publications

References 21 publications

The Golden Age of Transfer Hydrogenation

The Golden Age of Transfer Hydrogenation

Easy To Synthesize, Robust Organo‐osmium Asymmetric Transfer Hydrogenation Catalysts

Recent Advances in Osmium-Catalyzed Hydrogenation and Dehydrogenation Reactions

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